JPH05162108A - Manufacture of sintered material - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a sitered product wherein the influence of the contact surface between a product and a sinter supporting plate is excluded and the deformation due to own weight is not generated. CONSTITUTION:In a method for producing a sintered material wherein a mixture of raw material powder for sintering and binder containing organic high- molecular compounds is injection-molded to form a molded item and the molded item is formed into a sintered material by removing fat from the molded item to sinter it on a sinter supporting plate 4, removal of fat and sintering is performed using a separation supporting member 3 which removes the molded item from the supporting plate 4 to support it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple method for producing a sintered product by a powder injection molding method, which eliminates the influence of a sintered support plate.

[0002]

2. Description of the Related Art A powder injection molding method is used for sintering raw material powder 10
About 20% by weight of a binder containing a thermoplastic resin as a main component is added, kneaded, injection-molded in the same manner as ordinary plastic, and then the binder is removed by a method such as heating (called degreasing), and normal baking is performed. This is a manufacturing method in which a sintered product is obtained by sintering in the same manner as a sintered product. Compared with the usual manufacturing method in which a small amount of binder is added to sintering raw material powder, compression molding is performed, and sintering is performed, it has attracted attention in recent years because it can mass-produce products with complicated shapes with high dimensional accuracy, and is also used industrially. Is becoming available.

[0003]

The injection-molded body is usually made of
In addition to the product part, it consists of a sprue to guide the kneaded material to the product part, a runner called a runner, and a sprue called a gate connecting the product part and the runner. The gate is narrow to help separate product parts.
Therefore, after obtaining the molded body, the product, the runner, and the sprue are separated at the gate.

In the case of the powder injection molding method, the product portion thus obtained is loaded on a sintering support plate and degreased and sintered. However, at the time of this degreasing, since a large amount of thermoplastic resin is added to the molded body, the thermoplastic resin is softened by heating before it volatilizes, and the irregularities on the surface of the sintered support plate may be transferred. It is often seen. In addition, since a large amount of binder is added during sintering, there is a problem that shrinkage of 10% or more occurs, the product is deformed due to friction of the surface in contact with the sintering support plate, and the dimensional accuracy is significantly reduced. Exists.

In view of the above-mentioned drawbacks, the technical problem of the present invention is to provide a method for manufacturing a sintered product which eliminates the influence of the contact surface between the product and the sintered support plate and does not cause deformation due to its own weight. Especially.

[0006]

According to the present invention, a mixture of a raw material powder for sintering and a binder containing an organic polymer compound is injection molded to form a molded body, and the molded body is baked. In a method for producing a sintered body by degreasing and sintering on a binding support plate, degreasing and sintering are performed by using a separating support member that supports the compact by separating from the sintering support plate. A method of manufacturing a sintered product is obtained.

That is, according to the present invention, a raw material powder for sintering,
In a manufacturing method for obtaining a sintered product by injection molding a mixture with a binder containing an organic polymer as a main component, and degreasing and sintering, the product part is supported by a runner part to remove the degreasing and sintering support plate. A method for producing a sintered product, characterized by degreasing and sintering in a state where product parts are separated from each other, is obtained.

The present inventors have paid attention to the runner attached to the product part of the injection-molded article and devised and used it to solve the above-mentioned problems.

That is, by making the shape of the runner so that the product portion floats above the sintering support plate during loading on the sintering support plate, the product portion is transferred or sintered on the surface of the sintering support plate at the time of degreasing described above. It is possible to avoid deformation at the time and a significant decrease in dimensional accuracy. After the sintering, the product part can be easily separated from the runner at the gate part to obtain the product. According to this method, it is possible to easily degrease and sinter the powder injection molded body without being affected by the surface of the sintering support plate.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of an injection-molded article according to an embodiment of the present invention, and FIG. 2 is a side view.

Ni-Zn ferrite pre-calcined powder was prepared as a raw material powder for sintering, and Ni-Zn ferrite pre-calcined powder 8
16% by weight of a binder having an organic polymer compound as a main component was mixed with 4% by weight, kneaded and crushed to obtain a raw material for molding. Next, by injection molding, a molded product having a cylindrical product portion 1, a gate portion 2, and a runner portion 3 having a shape for supporting the product portion 1 shown in FIGS. 1 and 2 was obtained. The shape of the product is 20 mm in outer diameter, 16 mm in inner diameter, and 15 in height.
It is a cylinder of mm. Fifty of the compacts were stacked so that only the runner portion was in contact with the alumina sintered support plate.
Degreasing was performed at 0 ° C and sintering was performed at 1200 ° C. Obtained 50
The product part was separated from each sintered body, the upper and lower dimensions of the outer diameter were measured with a micrometer, and the average value of the dimensional difference between the upper and lower outer diameters and the standard stitch difference of the lower dimension of the outer shape were calculated. .. In addition, it was visually confirmed that the bottom surface was smooth.

Next, for comparison, the product part 1 from the molded product
Was separated and 50 pieces of the product part 1 alone were loaded on the alumina setter, degreased and sintered as in the example, and the same measurement was performed.

The measurement results thus obtained are shown in Table 1.
Shown in.

[0015]

[Table 1]

As is clear from Table 1, according to this embodiment, the deformation of the outer diameter due to the friction with the sintering support plate during sintering can be reduced to about 1/10 of that of the comparative example, and the outer portion of the lower part can be reduced. The variation in the diameter dimension can be reduced to about one third. Also,
It is also possible to prevent transfer on the surface of the sintered support plate during degreasing.

The present embodiment is not limited to the above embodiment. For example, instead of the Ni-Zn ferrite calcined powder, any other sinterable powder can be applied. Further, in the present embodiment, the injection molded product having four product parts was used, but it is naturally possible to use other number of products, and a larger number can reduce the amount of runners per product. Therefore, the cost can be reduced. Further, the shape of the runner may be changed as long as the product part can be separated from the sintering support plate, and can naturally be changed according to the product shape and the mold structure.

[0018]

According to the present invention, it is possible to easily eliminate the influence of the contact surface with the sintered support plate, which is a problem of the powder injection molded product, and improve the surface smoothness and the deformation amount. It is possible to reduce the size and improve the dimensional accuracy. Therefore, the post-processing of the sintered body can be reduced, and the production according to the present invention has a great effect of cost reduction as compared with the conventional method, and is extremely important industrially.

Further, in the case of a product having a complicated shape, which is a characteristic of the powder injection molding method, it is possible to solve the problem that the product is deformed due to its own weight during degreasing and sintering by loading it on the sintering support plate, which is complicated. Degreasing that does not cause deformation of shaped products,
Since sintering is possible, the original advantages of the powder injection molding method can be utilized. The present invention is also important in this respect.

[Brief description of drawings]

FIG. 1 is a plan view of an injection molded body according to an embodiment of the present invention.

FIG. 2 is a side view of the embodiment shown in FIG.

[Explanation of symbols]

 1 Product part 2 Gate 3 Runner 4 Sintered support plate

Claims (1)

[Claims] 1. A mixture of raw material powder for sintering and a binder containing an organic polymer compound is injection-molded to produce a molded body, and the molded body is degreased and sintered on a sintering support plate. In the method for producing a sintered body according to 1. above, degreasing and sintering are performed using a separation support member that separates and supports the molded body from the sintering support plate.